var list = new Array(1, 2, 3, 4, 5);

//优
list.forEach(function (item) {
  console.log(item)
})

//良
for (var i = list.length; i; i--) {
  console.log(list[i])
}

//一般
for (var i in list) {
  console.log(list[i])
}